A hybrid vehicle equipped with an engine and a motor has been known. In this hybrid vehicle, the motor works as a generator at the time of braking. Thereby, the braking of the hybrid vehicle is performed while obtaining the electric energy from the conversion of the kinetic energy of a vehicle. Hereinafter, to obtaining the electric energy using the motor defined as “regeneration”. This braking manner defined as “regenerative braking”.
In the hybrid vehicle, furthermore, electric energy obtained from the regenerative braking is stored in a high-pressure battery and is used at the time of acceleration, etc. Thereby, the hybrid vehicle can save the waste of energy than the conventional vehicle adopting the internal combustion engine. In the following explanation, the hybrid vehicle defined as “vehicle”.
FIG. 11 is a block diagram showing the construction relevant to the motor and high-pressure battery of the hybrid vehicle, which is disclosed in Japanese Patent Publication Hei 11-187577.
In FIG. 11, a motor 112 and a high-pressure battery 117 are connected each other through an inverter 116.
The electric energy stored in the high-pressure battery 117 is supplied to the motor 112 through the inverter 116 at the time of acceleration, and assists the power supply of the engine (not shown).
The motor 112, on the other hand, works as a generator at the time of braking. Thus, the electric energy (regenerative energy) obtained from the regeneration of the motor 112 is stored in the high-pressure battery 117 through the inverter 116.
In FIG. 11, the symbol TS indicates a temperature sensor which senses the temperature of the high-pressure battery 117. The symbol A indicates the ammeter, which senses the input-and-output current of the high-pressure battery 117. The symbol V indicates the voltmeter, which senses the voltage of the high-pressure battery 117. The symbol CU indicates the control-unit.
A hybrid vehicle is used under various ambient conditions, for example, from high temperature environment, i.e. desert, to the low temperature environment. But, there is an optimum temperature for operating each battery including the high-pressure battery 117.
When the electric current of high amount, for example, is discharged on the condition that the temperature of the high-pressure battery 117 is low, the voltage of the high-pressure battery 117 will be dropped because the reaction rate of the high-pressure battery becomes slow.
When the charge of the high-pressure battery 117 is carried out on the condition that the temperature of the high-pressure battery 117 is high, the deterioration of the high-pressure battery 117 will be advanced because the temperature of the high-pressure battery 117 becomes much higher.
For this reason, the charge/discharge of the high-pressure battery 117 is managed by the inverter 116 based on the map (power-saving map) shown in FIG. 12. In this occasion, the inverter 116 is controlled by the control-unit UC.
In the upper half of FIG. 12, the upper limit value of the current to be discharged from the high-pressure battery 117 is shown in longitudinal axis, and the temperature of the high-pressure battery 117 is shown in horizontal axis. In other words, upper half of FIG. 12 is a map used in order to control the upper limit of the electric energy to be discharged from the high-pressure battery 117 at each temperature.
In the lower half of FIG. 12, on the contrary, the upper limit of the electric energy to be charged on the high-pressure battery 117 is shown in longitudinal axis, and the temperature of the high-pressure battery 117 is shown in horizontal axis. In other words, the lower half of FIG. 12 is a map used in order to control the upper limit of the electric energy charged on the high-pressure battery 117 at each temperature.
The control-unit CU performs the management of the charge/discharge of the high-pressure battery 117 based on the upper limit value, which is determined with reference to the map (power saving map) according to the detected temperature of the high-pressure battery 117.
When the above-described management, the charge/discharge management, of the high-pressure battery 117 is performed, problems described below have been brought out.
(1) When the frequency of the charge/discharge of the high-pressure battery 117 is high, since the temperature of the high-pressure battery 117 does not drop easily owing to the thermal mass, the temperature of the high-pressure battery 117 will exceeds 45 degrees (maximum temperature) greatly.
(2) When the temperature of the high-pressure battery 117 exceeds 45 degrees and approaches to 50 degrees, the output current discharged from the high-pressure battery 117 will become small largely. In other words, the power outputted from the high-pressure battery 117 becomes low. Thus, a driver of the hybrid vehicle feels the powerlessness.
(3) When the temperature exceeds 45 degrees, since the total charge amount of electric energy obtained from the regenerative power generation will be restricted, the charge of the high-pressure battery 117 cannot be fully achieved. Thereby, the remaining amount in the high-pressure battery 117 becomes small because the discharge amount exceeds the charge amount. Thus, the driving power to be outputted from the motor becomes low.
The present invention mainly aims at providing a drive unit, which can prevent or control the temperature rise of the high-pressure battery.